The invention concerns a connection element for a composite hose having a spiral wound metal hose and an elastic outer casing, the connection element including a supporting sleeve having an outer thread adapted to the metal hose and engaging into spiraled depressions on the inner wall of the metal hose. The supporting sleeve also has an annular axial sealing surface bordering on the outer thread and spaced therefrom by a shoulder adapted to the outer casing of the composite hose. The invention is also directed to a process for connecting such a composite hose by setting an end of the composite hose to be connected on the supporting sleeve of the connection element, screwing the wound metal hose onto the outer thread of the supporting sleeve, and fastening the composite hose on the supporting sleeve by radial pressure.
Composite hoses having enclosed metal hose are often used in connection with high pressure conduits which must not only withstand a high interior pressure, but also a high exterior pressure in connection with low interior pressure.
An important area of application of such composite hoses lies in undersea drilling, for example submarine drilling for petroleum or natural gas. Here conduits are usually laid which include an entire bundle of hoses and conduits subjected to different stress (so-called umbilicals). For example, oil extracted from the oil bore hole, and at the same time, suspension, ethanol or extraction gas are conveyed into the oil bore hole. Moreover, as a rule, electrical conduits run in the umbilical pipelines for control of the boring apparatus.
Since such umbilical conduits are usually laid between a drilling rig and an oil bore hole situated on the bottom of the sea, the standards for the outer casing, but also on the individual conduits running therein, are high: The conduits must be flexible, which is generally only guaranteed by hose conduits, and they must at the same time withstand a high outer pressure, and indeed independently of whether an internal pressure of the same order of magnitude or only a negligible inner pressure is present. Depending upon the depth of the boring, a pressure difference of about 300 bar can arise without more, which must not lead to a collapse of the hose lines. Furthermore, the conduits must be so constructed that they do not corrode in aggressive salt water.
A composite hose of the type mentioned at the beginning, where the spiral wound metal hose consists of high grade steel and the outer casing consists of a thermoplastic, generally meets these standards.
Interfacing such composite hoses with attachment fittings or hose couplings is problematic, since in submarine use in particular, sea water must not be allowed to attack the enclosed, wound metal hose due to the danger of corrosion. At the same time, the interface must be pressure-tight toward the inside as well as toward the outside. Also, a certain tensile strength of the interface is indispensable. This problem exists throughout not only in connection with the outer casing of an umbilical hose, but also with the interface of the individual hoses passed in it, which as a rule are likewise composite hoses of the type mentioned at the beginning.
In addition, complicating matters is that the assembly of such connections must often take place on site and in part under severe conditions, for example in high seas, whereby a welding or soldering connection is then hardly producible, or not producible at all.
In U.S. Pat. No. 3,393,267, in another context, a connection element for a composite hose having a spiral wound metal hose and an elastic outer casing is proposed which includes a support sleeve having an outer thread adapted to the metal hose, which thread engages into the helically wound depressions of its interior wall, and an annular, radial sealing surface removed from it.
The supporting sleeve of this known connection element is set on the end of the composite hose to be joined, and the wound metal hose is screwed into the outer thread of the supporting sleeve. The composite hose is fastened by means of a screw sleeve to be placed on the connection element, into which a separate sealing ring is inserted. This sealing ring is deformed upon tightening the sleeve, such that the composite hose is pressed radially on the supporting sleeve, and at the same time the radial sealing surface is sealingly covered by the sealing ring in an axial direction. The outer thread of the supporting sleeve has the sole task of stretching the connection end of wound metal hose, and thus of guaranteeing that the elastic outer casing can in no event project so far beyond the end of the metal hose that it runs on the sealing surface.
For applications which require an interface of composite hoses on attachment fittings or hose couplings under high pressure differences and high tightness standards, there are, however, unsolved problems in connection with the prior art according to U.S. Pat. No. 3,393,267. The stretching of the wound metal hose by the outer thread of the known connection element takes place with deformation of the windings. Even the radial pressing for fastening the composite hose on this connection element presents the danger that the windings of the metal hose are additionally deformed. These deformations could result in the formation of sharp edges of the individual windings, which could possibly pierce the outer casing and thus destroy the sealing action. Furthermore, deformed windings can no longer hold up against high pressures, especially from the outside, so that there exists the danger of the composite hose collapsing in the area of the connection element. Finally, the windings of the metal hose no longer offer defined counter force against pressure at least when they are deformed, thus yielding to radial pressing force. A sealing of the connection element which is secure against high pressure is then no longer guaranteed.
Underlying the invention is therefore the objective of creating a connection element and a corresponding process with which a composite hose of the type mentioned at the beginning can be joined weld-free and solder-free but nonetheless stably, under defined conditions, tight and especially high pressure-resistant, to a fitting or coupling element.
In accordance with the invention, a connection element for a composite hose of the type mentioned at the beginning includes not only a supporting sleeve with an outer thread adapted to the metal hose which engages into the spiraled depressions of its interior wall, and an annular axial sealing surface bordering on the outer thread, but spaced from the outer thread by a shoulder, which sealing surface is adapted to the outer casing, but also a pressing element acting radially upon the supporting sleeve exclusively in the area of the sealing surface for all around sealing fastening of the outer casing on the sealing surface.
With such a connection element, it is possible to operate according to the process of the invention: The end of the composite hose to be connected is placed upon the supporting sleeve without prior preparation. The outer thread of the supporting sleeve is fitted to the inner-lying, wound metal hose and engages in the spiraled depressions of its inner wall without deforming it. Therefore, the composite hose can be screwed onto the supporting sleeve in a simple manner by means of its metal hose, and thus be fastened on it without tension. After this, the wound metal hose, and only this, is axially compressed, so that the outer casing is exposed projecting beyond the end of the metal hose. The outer casing thereby reaches beyond the end of the metal hose and the outer thread of the supporting sleeve on which this is fastened, and for its part can also be fastened pressure-tight on a sealing surface arranged axially behind the outer thread. With this construction, it can be prevented that the inner hose comes into contact with the surrounding medium, although it is attached pressure and tension-tight on the connection element free of welding and soldering.
Fastening the outer casing on the sealing surface takes place by means of radial pressing. Especially here, the invention offers particular advantages as the pressing only affects the outer casing of the composite hose, but not the wound metal hose. Thus, through a pressing of the wound metal hose its contours would possibly be deformed, and its pressure-tightness, in particular its capacity to resist bending, would thereby be strongly diminished. Since only the outer casing is pressed on the axial sealing surface, and the wound metal hose remains completely free of radial pressing forces, the problems of the prior art described above are eliminated.
The functions of xe2x80x9cresistance to tensile stressxe2x80x9d and xe2x80x9ctightnessxe2x80x9d of the connection element of the invention are completely separated: The wound metal hose takes over the resistance to tensile stress of the interface without endangering its resistance to shearing stress, and the outer casing of the composite hose takes care of tightness, wherein the pressing on the axial sealing surface takes place under defined and reproducible conditions. In this connection, the sealing action can be improved by appropriate contouring of the axial sealing surface, for example by a number of annular running ring grooves or recesses. Corresponding teeth or ring-shaped projections in the pressing element which a further increase the sealing action.
The process of the invention for joining composite hoses can be conducted at any desired point on a composite hose, since the hose is simply cut to length radially, for example with a saw. After screwing the inner-lying metal hose with the supporting sleeve, the axial compression of the metal hose can take place (optionally intermittently) by pushing the supporting sleeve into the outer casing of the composite hose. Subsequently, only the outer casing must still be attached on the sealing surface, preferably by means of a pressing sleeve, in order to complete the connection of the composite hose to an attachment fitting or a hose coupling.
Besides fastening the outer casing by means of a pressing sleeve, the outer casing can also be inserted into an annular space opening toward the connection hose and be attached in the annular space, for example likewise by pressing. The sealing surface of the invention is then part of the annular space.
The functional capacity of the connection element of the invention is further improved if the outer thread of the supporting sleeve is restricted in relation to the sealing surface by a catch or stop, which is preferably constructed as an annular ring-shaped front face. In this way, screwing on the wound metal hose is, first of all, limited in a defined manner. Secondly, the catch can assume a portion of the forces when the compression of the metal hose over the supporting sleeve takes place.
The spiral wound metal hose preferably comprises folded metal sections, wherein these in turn are preferably constructed as agraffe (hook) profiles. Agraffe profiles have, as is well known, a metallic sealing action with good flexibility, are very subject able to high pressure, as well as axially compressible and stretchable. Above all, the resistance to outside pressure, of particular interest here, is guaranteed by an agraffe profile.
The outer casing of the composite hose is preferably made of plastic, especially a thermoplastic. The outer casing can nevertheless comprise several layers of the same or even different material in order to increase its load-bearing capacity or, if need be, to guarantee a shielding.
The invention can likewise be used in joining individual composite hoses which run, for example, within an umbilical hose conduit, but also definitely serve to interface composite hoses which convey in themselves an entire bundle of individual hoses or conduits. Particularly to be emphasized, in any case, is the simplicity of the solder-free and weld-free assembly, the resistance to tensile stress and pressure safety, especially outside pressure security of the connection of the invention.